THE MOLECULAR BASIS OF INHERITANCE
DNA MAKES RNA MAKES PROTEIN
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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TAC
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UAC
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ATG
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AUG
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Detailed explanation-1: -Methionine is specified by the codon AUG, which is also known as the start codon. Consequently, methionine is the first amino acid to dock in the ribosome during the synthesis of proteins. Tryptophan is unique because it is the only amino acid specified by a single codon.
Detailed explanation-2: -Genetic code table. Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons. AUG is the codon for methionine, and is also the start codon.
Detailed explanation-3: -The codon AUG both codes for methionine and serves as an initiation site: the first AUG in an mRNA’s coding region is where translation into protein begins. The other start codons listed by GenBank are rare in eukaryotes and generally codes for Met/fMet.
Detailed explanation-4: -The AUG codon is usually within the context of a slightly larger sequence, called the Kozak consensus sequence, which generally has the sequence GCCACCAUGG (the underlined adenine can also be a guanine). AUG codes for the amino acid methionine, and so all protein translation begins with methionine. Figure 3.17.